Known in the art are various types of volumetric metering apparatuses for bulk materials. Thus known in the art is an apparatus (SU, A, 598822) comprising a vertically extending receiving hopper having a guide funnel in the bottom part thereof and a disc with a discharge opening mounted therebetween for rotation about vertical axis. Rotation of the disc progressively disrupts equilibrium of material over the discharge opening within a so called vault or bridge, and the material moves under gravity through the discharge opening into the guide funnel.
This apparatus is deficient in a low metering accuracy because dimensions of the vaults, hence quantity of the material passing through the discharge opening per unit of time largely vary and are probabilistic.
Also known in the art is an apparatus (SU, A, 401616) comprising a vertically extending receiving hopper having a disc with a discharge opening provided in the bottom part thereof for rotation about vertical axis and a tripping knife mounted above the discharge opening in an inclined position with respect to the disc surface.
This apparatus is deficient in a low metering accuracy because the tripping knife overcoming resistance of the bulk material would deform it thus causing irreversible and uncontrollable changes in density.
In addition, the inclined surface of the tripping knife initiates settling of the material in the hopper over the discharge opening thus resulting in inadvertent discharges of the material which is also detrimental to the metering accuracy.